Stack Manageability
01.08.2024, Eric Bergerarstechnica.com
NASA's Lunar Gateway has a serious problem with visiting spacecraft.
“These defects can cause unexpected reboots of onboard computers.”
Remember the Lunar Gateway? If not, you can be forgiven, as the program continues to be debated by NASA planners, and it's still not entirely clear what purpose a lunar space station would serve.
The Gateway (a small space station that would fly in a halo orbit around the Moon and spend most of its time away from the lunar surface) was originally scheduled to launch in 2022. Apparently, that didn't happen, and now, according to new report from the U.S. Government Accountability Officethe space agency doesn't expect to launch the initial elements of the Gateway until at least December 2027. The base cost estimate is $5.3 billion.
NASA’s current plans call for the Gateway to be used as part of the Artemis IV mission, which is currently scheduled for September 2028. Unfortunately, the Gateway’s current launch date is already three months later than it needs to be to support Artemis IV, the second mission to land humans on the moon. But that’s OK. There are a lot of other moving parts for that mission, so launching anytime this decade would be a win.
In the report [Счетной палаты] A helpful graphic is included to explain the complex sequence of events that must occur in order for the Gateway to be used in the Artemis IV mission:
1. Launch of the initial segments of the Gateway, the power and propulsion module, and the habitation module into halo orbit around the Moon;
2. Launch of the SpaceX Dragon XL spacecraft to deliver cargo to the Gateway;
3. Launching multiple SpaceX Starship spacecraft to refuel the lunar Starship, which will then fly to and dock with the Gateway;
4. Launch of the NASA Space Launch System rocket with four astronauts on board the Orion spacecraft, as well as another Gateway module – International Habitat;
5. After launch, Orion separates from the rocket and docks with this module;
6. Orion tows International Habitat to the Gateway and docks; crew transfers to the Gateway;
7. Two crew members board the Lunar Starship and travel to the Moon for six days;
8. The Lunar Starship returns to the Gateway, and the four astronauts return to Earth inside Orion.
The report cautiously notes that the plan is quite complex and carries serious risks of being delayed.
“This mission will be complex because NASA will need to coordinate seven agency programs, multiple contractors that support those programs, and international partners to execute the mission,” the report said. “It will also be the first launch of an upgraded version of the Space Launch System rocket.”
Difficulties of development
The report also notes that the Gateway program is facing some pretty serious technical challenges. One of them involves a faulty network chip that provides communications throughout the lunar space station. Its failure could cause a host of problems on board the Gateway.
“For example, these flaws could cause the onboard computers to restart unexpectedly,” the report says. “If the network is not functioning properly, it could result in loss of control of the Gateway. Program managers are also concerned that they may discover more flaws in the communications network based on the number already discovered.”
Another risk is what's called “stack controllability.” This essentially means that because SpaceX's Lunar Starship is much more massive than the Gateway, when it docks with the space station, the Gateway's power and propulsion element (PPE) will not be able to maintain the proper orientation of the entire stack (the Gateway with the docked spacecraft).
“Program management estimates that the Starship lunar lander mass is approximately 18 times greater than the value NASA used to develop the PPE handling parameters,” the report says. “According to NASA's systems engineering guidance, late requirements and design changes could result in increased costs and schedule delays.”
The report also contains some sobering conclusions about the Lunar Gateway’s potential usefulness for Mars missions. In the past, NASA officials have talked about the Gateway as a staging area for spacecraft and fuel for human missions to the surface of Mars. However, the “stack manageability” problem poses serious limitations for accommodating large vehicles for Martian transit. Moreover, the Gateway’s planned 15-year lifespan may not be long enough to support Mars missions.
“Gateway could exceed its planned 15-year orbital lifetime as early as 2042, when human missions to Mars are just beginning,” the report says.
Overall, the report concludes that the Gateway is significantly behind schedule and has limited utility for landing on the Moon and Mars. The report says that it will be difficult to implement the Gateway while trying to build a lunar exploration program. But otherwise, things are going well.
Translation: Alexander Tarlakovsky (blog tay-ceti)
Original: NASA's Lunar Gateway has a large visiting vehicles problem
Additional Information: Robert Zubrin – NASA's Worst Plan Yet
